Viscous fluid coupling

Abstract

A viscous fluid coupling includes a housing rotatably supported to a drive shaft of an engine. An operation plate set in the housing divides a space of the housing into a reservoir and an operation chamber. The operation plate has a communication hole communicating the reservoir and the operation chamber. A rotor fixed to the drive shaft is disposed in the operation chamber. A valve mechanism installed to the operation plate to close and open the communication hole according to ambient temperature of the housing. A driven wheel fixed to the housing is located between the operation plate and the rotor. A torque transmitting section includes a first annular projection concentrically formed on the driven wheel and a plurality of second annular projections concentrically formed on the rotor. The first annular projections are overlappedly adjacent to the second annular projections so as to establish fluid coupling therebetween through the viscous fluid.

What is claimed is:  
     
       1. A viscous fluid coupling connected to an engine, comprising: a drive shaft connected to a rotation shaft of the engine; a housing rotatably supported to said drive shaft; 
       an operation plate set in said housing and dividing a space defined by said housing into a reservoir and an operation chamber, said operation plate comprising a communication hole communicating the reservoir and the operation chamber;  
       viscous fluid in the reservoir and the operation chamber;  
       a rotor disposed in the operation chamber and being fixed to said drive shaft;  
       a valve mechanism closing and opening the communication hole according to ambient temperature of said housing to control a flow rate of said viscous fluid from the reservoir to the operation chamber;  
       a driven wheel fixed to said housing and being located between said operation plate and said rotor; and  
       a torque transmitting section including a plurality of first annular projections concentrically formed on an outer peripheral portion of said driven wheel and a plurality of second annular projections concentrically formed on an outer peripheral portion of said rotor, the first annular projections being overlappedly adjacent with the second annular projections and being fluidly coupled with the second annular projections through said viscous fluid, a part of said torque transmitting section being located inside of an outermost portion of the reservoir in a radial direction.  
     
     
       2. A viscous fluid coupling as claimed in claim  1 , wherein said torque transmitting section is located at a position higher in height level than a fluid level of said viscous fluid when the engine is stopped. 
     
     
       3. A viscous fluid coupling as claimed in claim  1 , wherein said rotor comprises lightening holes which penetrate said rotor in its thickness direction, the lightening holes being located at a position higher in height level than a fluid level of said viscous fluid when the engine is stopped. 
     
     
       4. A viscous fluid coupling as claimed in claim  1 , wherein the first annular projections and the second annular projections are arranged such that an overlapped amount therebetween at an outer side in the diametrical direction is smaller than the overlapped amount at an inner side in the diametrical direction. 
     
     
       5. A viscous fluid coupling as claimed in claim  1 , wherein said driven wheel is installed to said housing so that an auxiliary chamber is located at a position of the communication hole. 
     
     
       6. A viscous fluid coupling as claimed in claim  1 , wherein said operation plate is fixed to said housing through caulking portions of said housing, said driven wheel having an annular groove for receiving the caulking portion. 
     
     
       7. A viscous fluid coupling as claimed in claim  1 , wherein said operation plate is fixed to said housing through caulked portions by means of caulking connection. 
     
     
       8. A viscous fluid coupling as claimed in claim  7 , wherein the caulked portions are formed at equal intervals. 
     
     
       9. A viscous fluid coupling as claimed in claim  1 , wherein the communication hole is communicated with said torque transmitting section through an auxiliary chamber formed between said operation plate and said driven wheel. 
     
     
       10. A viscous fluid coupling as claimed in claim  9 , wherein the auxiliary chamber comprises a plurality of auxiliary chambers which are communicated with said torque transmitting section through passages, respectively, the passages being located at positions which are different in distance from an axial center of said driven wheel. 
     
     
       11. A viscous fluid coupling as claimed in claim  9 , wherein the auxiliary chamber is formed into a sector shape. 
     
     
       12. A viscous fluid coupling as claimed in claim  9 , wherein a cross-sectional area of the auxiliary chamber is greater than the cross-sectional area of the communication hole of said operation plate. 
     
     
       13. A viscous fluid coupling as claimed in claim  1 , wherein said driven wheel is overlapped with said operation plate, said driven wheel and said operation plate being fixed to said housing by means of a plurality of bolts. 
     
     
       14. A viscous fluid coupling as claimed in claim  1 , wherein said operation plate is fixed to said housing by means of caulking connection, at least one annular groove for the caulking connection is circumferentially formed on a surface of said driven wheel facing with said operation plate. 
     
     
       15. A viscous fluid coupling as claimed in claim  1 , wherein said rotor comprises a lightening hole. 
     
     
       16. A viscous fluid coupling as claimed in claim  1 , wherein said valve mechanism comprises a valve plate fittingly set on said operation plate and a coiled bimetal for driving the valve plate. 
     
     
       17. A viscous fluid coupling as claimed in claim  1 , wherein said housing comprises a housing body member and a cover member.